BackboneJS-Model hasChanged

BackboneJS-Model hasChanged

<!DOCTYPE html>
   <head>
      <title> Model Example</title>
         <script src="https://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" type="text/javascript"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" type="text/javascript"></script>
         <script type="text/javascript">
            var person = new Backbone.Model({
               name: 'john'
            });

            document.write('Has name changed (before set) = ' + person.hasChanged());

            person.set('name', 'smith', {silent: true});
            document.write('<br>Has name changed (after set) =' + person.hasChanged());
         </script>
   </head>
   <body></body>
</html>